(a) Field of the Invention
The present invention relates to liquid crystal displays (LCDs) and manufacturing methods thereof.
(b) Description of the Related Art
In LCDs, an electric field is applied to liquid crystal material injected between two substrates, an array substrate and a counter substrate, arranged substantially parallel to one another with a predetermined gap therebetween. Formed on the array substrate are a plurality of gate lines disposed parallel to one another, and a plurality of data lines insulated from and crossing the gate lines. A plurality of pixel electrodes are formed corresponding to respective regions defined by the intersecting data lines and gate lines. Furthermore, a thin film transistor (TFT) is provided near each of the intersections of the gate lines and the data lines. Each pixel electrode is connected to a data line via a corresponding TFT, the TFT serving as a switching device therebetween.
Such TFT-LCDs are formed by laying a plurality of thin films, one at a time, and etching the same. However the films tend to break open in certain areas, causing a disconnection of the portion of the films. To prevent this, the data lines are doubled at portions where they overlap the gate lines. A metal layer may also be deposited and patterned either over or under the data lines, following the pattern of the same to form repair lines.
In the first method, the data lines disconnected in areas other than the intersection require additional lines to repair the damaged portion. Furthermore, a laser junction process used to repair the disconnected data lines may not be easily applied to high-resolution displays.
Since the second method deposits and patterns the metal layer to form the repair lines and subsequently deposits and etches an insulating layer to connect the repair lines to the data lines, the overall LCD manufacturing process becomes complicated due to the additional steps.
An LCD having a couple of gate lines in a pixel may be used to prevent defects by the disconnection of the gate line. The LCD includes a couple of the gate lines parallel to each other, and a connecting line that links the gate lines. A secondary line to repair the disconnected data lines is formed in parallel with the connecting line, and a data line overlaps the secondary line. Since the secondary line and the data line are electrically connected to each other, data signals are transmitted through the secondary line when the data line is disconnected.
However, the narrow space between the secondary line and the connecting line increases a coupling capacitance between the data line and the connecting line and delays the digital signal. Furthermore, the connecting line and the secondary line may be short-circuited by conductive particles.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide an LCD and a manufacturing method thereof in which a repair line structure is used to minimize defects caused by the disconnection of data lines without introducing additional steps.
It is another object of the present invention to provide an LCD and a manufacturing method thereof in which a light-blocking layer is substituted with repair lines, thereby improving the aperture ratio.
It is another object of the present invention to provide a structure having double gate lines, which prevents signal delays and short-circuit defects of a data line and a gate line.
It is another object of the present invention to provide a structure that keeps an aperture ratio from decreasing, in a structure having double gate lines.
To achieve the above objects, the present invention provides an LCD and a manufacturing method thereof in which repair lines, substituting open-line data lines, are made of a metal layer for gate lines on the same layer as the gate lines, and are separately formed on either side of the gate lines. Data lines are formed intersecting gate lines on an insulating layer that covers the repair lines.
Further, a plurality of repair lines, substituting an open-line data line, are made of a metal layer for gate wires on the same layer as the gate lines, and are divided into a plurality of portions by the gate lines and overlap pixel electrodes.
The repair lines are electrically connected to the data lines to transmit data signals when the data lines are disconnected.
Furthermore, the repair lines overlap the edges of the pixel electrodes to shield the light-leakage area by fringe fields near the edges of the pixel electrodes.
The width of the repair lines is larger than that of the data lines.
The data lines are divided into two lines at the portion where the data lines cross the gate lines so when one of the lines is disconnected, signals can be transmitted through the other line.
The repair lines and the data lines can be directly, or indirectly, connected by another connecting means.
The connecting means includes transparent conductive patterns which are made of the same material as the pixel electrodes. These transparent conductive patterns are connected to separate repair lines and to the data line on either side of the gate line. Even in the case where the repair lines connect the data lines directly, transparent conductive patterns may be connected to the data lines on either side of the intersecting portions of the data lines and the gate lines. The transparent conductive patterns can act as a path for signals when the data lines become disconnected at the intersections.
In a twisted-nematic LCD or a vertically-aligned LCD having different liquid crystal disclination widths at both sides of the pixels, the pixel electrode is overlapped on both edges of the repair line with the overlapping edges having different widths.
The edges of the pixel electrode overlap the gate lines.
The repair lines or the gate lines overlapping the edges of the pixel electrodes prevent light-leakage from occurring around the edges of the pixel and increase the aperture ratio.
In the LCD of this structure, the repair line is laid in the process of forming the gate lines; and the transparent conductive connecting patterns are formed in the process of forming the transparent pixel electrodes.
As a result, the repair lines and connecting patterns for repairing the data line defects are formed without an additional process, which simplifies the manufacturing process.
In another embodiment of the present invention having double gate lines formed in parallel with each other in a horizontal direction, a connecting line that connects one of the gate lines to the other of the gate lines is vertically formed, passing across the center of a pixel region which is defined by the double gate lines and the data lines.
As described, since the connecting line is located far away from the data line and the secondary line, it is quite rare that the data signals affect the connecting line and conductive impurities short-circuit the connecting line and the secondary line.
The connecting line may not necessarily be formed in every pixel region.
A projecting portion, which is enhanced from the gate line of the pixel region having no connecting line, is formed to increase the overlapping area of the pixel electrode and the gate line.
The pixels where the connecting lines are formed may be arranged on the whole substrate at their options. However, it is required that the number of the pixels, where the connecting lines are formed, are larger than the number of the pixels where the connecting lines are not formed. It is required that the ratio of the number of the pixels having the connecting lines to the number of the pixels having no connecting lines is more than 1:3.
It is also possible that the connecting line is formed under the data line, not in the center of the pixel region, and the secondary lines are formed under the data lines under which the connecting line is not formed. In this case, it is required that the number of the connecting lines are smaller than the number of the secondary lines, and the ratio is preferably 1:10.
A connecting means, which links both ends of the secondary lines on the both sides with respect to the gate line to the data line, may be included, and the connecting means may be made of a transparent conductive material.
In this structure, the connecting line laid under the data line increases the aperture.